4-Up
Since the Micro Collection line was to be at
such a small scale, it was easier for Kenner's sculptors to create its prototypes in a blow-up size.
Therefore, Micro Collection figures were sculpted at four times the size they were intended to be produced
at. The resulting hardcopies were therefore also
four times the normal size and they are often referred to as 4-ups. It
can also be called a 4:1 (pronounced four-to-one).

The typical 4-up is made of a casting material known as Dynacast, and is either painted or unpainted. Painted examples were typically used as either paint masters or display models for shows such as Toy Fair.
The unpainted examples could have been used for corrections or were simply
extras. However, one of these unpainted 4-ups, the one with no flaws or
blemishes, was taken and used as a tooling master. These tooling masters were
put into a machine called a pantograph. The
pantograph would create a steel mold that was 1/4
the size of the tooling master, or in other words, the regular production size
of a Micro figure. The steel molds were then used for mass production.

Micro 4-ups
have recently gained more appeal to collectors as they're large, statuesque, and provide an essential look inside the toy production process.
Also, while the original sculpts are 4:1, they are never referred to as
4-ups. They are simply called sculpts or original sculpts and belong in a league
all their own.